VMware has not released the session recordings yet on their website so registered attendees can watch them from a PC, if you go the page for session playback on the VMworld.com website they only have up to 2014 listed there. I tried changing the 2014 URL to 2015 but the page is not found so I suspect they are still working on getting that page created or are waiting until after VMworld in Barcelona to end to post them. However if you have the VMworld 2015 mobile app on your tablet or phone you can access all of the session recordings right now.
Just load the app and login to it (must be a registered attendee) and then click the Videos link in the menu sidebar. You’ll then see all the sessions listed alphabetically for you to choose from. One thing to note is that the VMworld app only supports portrait viewing of the videos so if you rotate your device to landscape it won’t switch to it and you are stuck watching it in portrait which can be fairly small on a phone. However if you hit the upper arrow button when the app is playing it will open in a browser which will rotate to landscape mode (lower arrow button expands it in the app which is still portrait).
However you will be prompted for credentials from mediasite.com if you do that and your VMworld login won’t work so you can’t watch it that way. I’m guessing they hard-coded some credentials in the app that has access to the videos on mediasite.com so you’ll just have to wait until they post them on the VMworld.com page to watch them from a PC (or download BlueStacks).
It looks like you can also do this if you go to the VMworld Content Catalog and click on a session, there will be a Media link on the right sidebar to playback the session.